It is conventional practice to produce peg board, rock lath, and similar perforated plates by pressing a sheet of filamentary material held together by a binder such as hydraulic cement between a pair of platens one of which is provided with an array of pins. Traditionally the mat is carried on a transport tray that is formed with an array of holes having inside diameters corresponding to the outside diameters of the pin array on the upper press platen. The transport tray is exactly positioned under the array of pins so that when the platens are closed the pins pass through the mat and through the tray, therefore producing a hard board having an array of perforations exactly corresponding to the array of pins and holes on the platen and tray.
This arrangement has the considerable disadvantage that it is necessary to control the motion of the transport tray with extreme precision. This is so because it is absolutely essential that the holes in the transport tray, which acts as a multiple dies, are aligned perfectly with the pins on the press platen. Otherwise damage to the press will occur. These transport trays are usually relatively thick metal plates so that if it is desired to change the diameter of the perforations formed in the board it is necessary to replace the plates as well as the pins, a relatively expensive proposition. Thus the necessary control and transport system is very expensive as is changeover to a different type of board.